1. Field of the Invention
The present invention relates to a sheet material identifying device for identifying the kind of sheet material and an image forming apparatus having the sheet material identifying device.
2. Related Background Art
Conventionally sheet material identifying device for identifying sheet materials receive attention in various technical fields. For example, the number of kinds of paper used for printers has increased year by year and thus devices for identifying the kind of paper (overhead transparencies, photo glossy papers, coated papers or plain papers) have grown in demand. This point will be described below.
With the development of inkjet technology, ink-jet printers are capable of printing photos with high image quality. In this case, it is important to control an amount of ink discharged from an ink-jet printer to a sheet and control the penetration of ink, the control being made by treatment on a surface of a sheet. Hence, the ink discharge ports of ink-jet printers have been improved to be finer. Also regarding papers, ink penetration control has been improved by performing coating on a surface of a dedicated paper for high image quality. For this reason, a dedicated paper for high image quality is used for printing a high-quality image and a plain paper is used for ordinary printing. The dedicated paper for high image quality is inevitably expensive due to surface treatment. Depending upon desired image quality, several grades of papers are available. Prices correspond to the grades of papers. Further, overhead transparencies, though not being papers, are still used as a kind of printer paper. In this way, the variety of printer papers has become wider.
With such a variety of papers, it is necessary to change the setting of a printer for each kind of paper. When a setting is manually changed by the user, in the case where the user mistakenly selects a kind of paper or mistakenly makes a setting for paper, characters may be simply printed on an expensive dedicated paper for high picture quality.
Hence, the necessity for means and a device for identifying the kind of paper has become a focus of attention in recent years and the development of the means and device has been advanced.
In ink-jet printers currently on the market, devices for identifying the kind of paper emit light on a surface of a sheet by using a light-emitting element and detects reflected light and scattered light by using a light-receiving element. When a specific light beam is emitted to the surface of the sheet, reflected light and scattered light are varied due to gloss and roughness on the surface. The above-described device identifies the kind of paper in compliance with this principle. This technique is disclosed in U.S. Pat. No. 6,291,829.
However, such an optically detecting method requires a light-emitting source and detecting means including a lens for detecting reflected light, scattered light and transmitted light, resulting in a large number of components constituting the sheet detecting device.